SiC composite substrate and method for manufacturing same

A method for manufacturing an SiC composite substrate comprising a polycrystalline SiC substrate and a monocrystalline SiC layer thereon, comprising the steps of:

• forming a monocrystalline SiC thin film on one major surface of a support substrate,
• mechanically working the surface of the monocrystalline SiC thin film for roughening, and removing defects caused by mechanical working, to form a monocrystalline SiC layer having a surface which is more rugged than the surface of the layer adjacent to the support substrate, the rugged surface being composed of oblique surface segments which are randomly oriented with reference to a normal direction to the surface of the layer adjacent to the support substrate,
• depositing polycrystalline SiC on the rugged surface of the monocrystalline SiC layer by chemical vapor deposition, thereby forming a polycrystalline SiC substrate wherein the close-packed planes of polycrystalline SiC crystals are randomly oriented with reference to a normal direction to the surface of the monocrystalline SiC layer adjacent to the support substrate, and
• thereafter physically and/or chemically removing the support substrate.